1. Field of the Invention
The present invention relates to improvements in a lumbar support applied to a seat back of a vehicular seat, and more particularly to a lumbar support apparatus which supports a lower back or lumbar section of a seated occupant so as to improve the comfort of the occupant.
2. Description of the Prior Art
A variety of lumbar support apparatuses have been proposed and put into practical use in order to reduce fatigue of a seated occupant during long drives. A typical lumbar support apparatus is disclosed, for example, in Japanese Utility Model Provisional Publication No. 51-163224 and Japanese Patent Publication No. 57-19965. Such a lumbar support apparatus is arranged such that the hardness of a cushion member in the seat back is continuously variable by controlling a screw adjusting device connected to a spring member in the seat back. With the conventional hardness adjusting device, the hardness of the seat back is continuously variable at a location corresponding to the lumbar portion of the seated occupant while at the same time the impact durability is improved.
However, the conventional lumbar support apparatus suffers drawbacks, since the assembly operation is complicated, large amount of parts are required and installation involves many steps. Therefore, this system is costly to produce.